WHAT follows now is speculation, speculation often far-fetched, which each will according to his particular attitude acknowledge or neglect. Or one may call it the exploitation of an idea out of curiosity to see whither it will lead.

Psycho-analytic speculation starts from the impression gained on investigating unconscious processes that consciousness cannot be the most general characteristic of psychic processes, but merely a special function of them. Metapsychologically expressed, it asserts that consciousness is the functioning of a particular system which may be called Bw. Since consciousness essentially yields perceptions of excitations coming from without and feelings (Empfindungen) of pleasure and pain which can only be derived from within the psychic apparatus, we may allot the system W-Bw.1 (= perceptual consciousness) a position in space. It must lie on the boundary between outer and inner, must face towards the outer world, and must envelop the other psychic systems. We then note that in this assumption we have ventured nothing new, but are in agreement with the localising tendencies of cerebral anatomy, which places the seat of consciousness in the cortical layer, the outermost enveloping layer of the central organ. Cerebral anatomy does not need to wonder whyanatomically speakingconsciousness should be accommodated on the surface of the brain, instead of being safely lodged somewhere in the deepest recesses of it. Perhaps we may carry matters a little further than this in our deduction of such a position for our system W-Bw.

Consciousness is not the only peculiar feature that we ascribe to the processes in this system. Our impressions gained by psycho-analytic experience lead us to the supposition that all excitation processes in the other systems leave in them permanent traces forming the foundations of memory-records which have nothing to do with the question of becoming conscious. They are often strongest and most enduring when the process that left them behind never reached consciousness at all. But we find it difficult to believe that such lasting traces of excitation are formed also in the system W-Bw. itself. If they remained permanently in consciousness they would very soon limit the fitness of the system for registration of new excitations;2 on the other hand, if they became unconscious we should be confronted with the task of explaining the existence of unconscious processes in a system whose functioning is otherwise accompanied by the phenomenon of consciousness. We should, so to speak, have gained nothing and altered nothing by our supposition which relegates to a special system the process of becoming conscious. Though this may not be an absolutely binding consideration, it may at any rate lead us to conjecture that becoming conscious and leaving behind a memory-trace are processes incompatible with each other in the same system. We should thus be able to say: in the system Bw. the process of excitation becomes conscious but it leaves behind no lasting trace; all the traces of it on which memory relies would come about in the next systems inwards from the propagation of the excitation on to them. It is on these lines that the scheme is sketched which I inserted into the speculative section of my Traumdeutung in 1900. If one reflects how little we know from other sources about the origin of consciousness the pronouncement that consciousness arises in the place of the memory-trace must be conceded at least the importance of a statement which is to some extent definite.

The system Bw. would thus be characterised by the peculiarity that the excitation process does not leave in it, as it does in all other psychic systems, a permanent alteration of its elements, but is as it were discharged in the phenomenon of becoming conscious and vanishes. Such a departure from the general rule requires an explanation on the ground of a factor which comes into account in this one system only: this factor which is absent from all other systems might well be the exposed situation of the Bw. systemits immediate contact with the outer world.

Let us imagine the living organism in the simplest possible form as an undifferentiated vesicle of sensitive substance: then its surface, exposed as it is to the outer world, is by its very position differentiated and serves as an organ for receiving stimuli. Embryology, repeating as it does the history of evolution, does in fact show that the central nervous system arises from the ectoderm; the grey cortex of the brain remains a derivative of the primitive superficial layer and may have inherited essential properties from this. It would then be easily conceivable that, owing to the constant impact of external stimuli on the superficies of the vesicle, its substance would undergo lasting alteration to a certain depth, so that its excitation process takes a different course from that taken in the deeper layers. Thus a rind would be formed which would finally have been so burned through by the effects of stimulation that it presents the most favourable conditions for the reception of stimuli and is incapable of any further modification. Applying this idea to the system Bw., this would mean that its elements are not susceptible of any further lasting alteration from the passage of the excitation, because they are already modified to the uttermost in that respect. But they are then capable of giving rise to consciousness. In what exactly these modifications of the substance and of the excitation process in it consist many views may be held which as yet cannot be tested. It may be assumed that the excitation has, in its transmission from one element to another, to overcome a resistance, and that this diminution of the resistance itself lays down the permanent trace of the excitation (a path): in system Bw. there would no longer exist any such resistance to transmission from one element to another. We may associate with this conception Breuers distinction between quiescent (bound) and free-moving investment-energy in the elements of the psychic systems;3 the elements of the system Bw. would then convey no bound energy, only free energy capable of discharge. In my opinion, however, it is better for the present to express oneself as to these conditions in the least committal way. At any rate by these speculations we should have brought the origin of consciousness into a certain connection with the position of the system Bw. and with the peculiarities of the excitation process to be ascribed to this.

We have more to say about the living vesicle with its receptive outer layer. This morsel of living substance floats about in an outer world which is charged with the most potent energies, and it would be destroyed by the operation of the stimuli proceeding from this world if it were not furnished with a protection against stimulation (Reizschutz). It acquires this through its outermost layerwhich gives the structure that belongs to living matterbecoming in a measure inorganic, and this now operates as a special integument or membrane that keeps off the stimuli, i. e. makes it impossible for the energies of the outer world to act with more than a fragment of their intensity on the layers immediately below which have preserved their vitality. These are now able under cover of the protecting layer to devote themselves to the reception of those stimulus masses that have been let through. But the outer layer has by its own death secured all the deeper layers from a like fateat least so long as no stimuli present themselves of such a strength as to break through the protective barrier. For the living organism protection against stimuli is almost a more important task than reception of stimuli; the protective barrier is equipped with its own store of energy and must above all endeavour to protect the special forms of energy-transformations going on within itself from the equalising and therefore destructive influence of the enormous energies at work in the outer world. The reception of stimuli serves above all the purpose of collecting information about the direction and nature of the external stimuli, and for that it must suffice to take little samples of the outer world, to taste it, so to speak, in small quantities. In highly developed organisms the receptive external layer of what was once a vesicle has long been withdrawn into the depths of the body, but portions of it have been left on the surface immediately beneath the common protective barrier. These portions form the sense organs, which essentially comprise arrangements for the reception of specific stimuli, but also possess special arrangements adapted for a fresh protection against an overwhelming amount of stimulus, and for warding off unsuitable kinds of stimuli. It is characteristic of them that they assimilate only very small quantities of the outer stimulus, and take in only samples of the outer world; one might compare them to antennae which touch at the outer world and then constantly withdraw from it again.

At this point I shall permit myself to touch cursorily upon a theme which would deserve the most thorough treatment. The Kantian proposition that time and space are necessary modes of thought may be submitted to discussion to-day in the light of certain knowledge reached through psycho-analysis. We have found by experience that unconscious mental processes are in themselves timeless. That is to say to begin with: they are not arranged chronologically, time alters nothing in them, nor can the idea of time be applied to them. These are negative characteristics, which can be made plain only by instituting a comparison with conscious psychic processes. Our abstract conception of time seems rather to be derived wholly from the mode of functioning of the system W-Bw., and to correspond with a self-perception of it. In this mode of functioning of the system another form of protection against stimulation probably comes into play. I know that these statements sound very obscure, but I must confine myself to these few hints.

So far we have got to the point that the living vesicle is equipped with a protection against stimuli from the outer world. Before that, we had decided that the cortical layer next to it must be differentiated as the organ for reception of external stimuli. But this sensitive layer (what is later the system Bw.) also receives excitations from within: the position of the system between outer and inner and the difference in the conditions under which this receptivity operates on the two sides become deciding factors for the functioning of the system and of the whole psychic apparatus. Towards the outer world there is a barrier against stimuli, and the mass of excitations coming up against it will take effect only on a reduced scale; towards what is within no protection against stimuli is possible, the excitations of the deeper layers pursue their way direct and in undiminished mass into the system, while certain characteristics of their course produce the series of pleasure-pain feelings. Naturally the excitations coming from within will, in conformity with their intensity and other qualitative characteristics (or possibly their amplitude), be more proportionate to the mode of operation of the system than the stimuli streaming in from the outer world. Two things are, however, decisively determined by these conditions: first the preponderance over all outer stimuli of the pleasure and pain feelings, which are an index for processes within the mechanism; and secondly a shaping of behaviour towards such inner excitations as bring with them an overplus of pain. There will be a tendency to treat them as though they were acting not from within but from without, in order for it to be possible to apply against them the defensive measures of the barrier against stimuli (Reizschutz). This is the origin of projection, for which so important a part is reserved in the production of pathological states.

I have the impression that by these last considerations we have approached nearer to a comprehension of the supremacy of the pleasure-principle, but we have not attained to an explanation of those cases which are opposed to it. Let us therefore go a step further. Such external excitations as are strong enough to break through the barrier against stimuli we call traumatic. In my opinion the concept of trauma involves such a relationship to an otherwise efficacious barrier. An occurrence such as an external trauma will undoubtedly provoke a very extensive disturbance in the workings of the energy of the organism, and will set in motion every kind of protective measure. But the pleasure-principle is to begin with put out of action here. The flooding of the psychic apparatus with large masses of stimuli can no longer be prevented: on the contrary, another task presents itselfto bring the stimulus under control, to bind in the psyche the stimulus mass that has broken its way in, so as to bring about a discharge of it.

Probably the specific discomfort of bodily pain is the result of some local breaking through of the barrier against stimuli. From this point in the periphery there stream to the central psychic apparatus continual excitations such as would otherwise come only from within.4 What are we to expect as the reaction of the psychic life to this invasion? From all sides the charging energy is called on in order to create all round the breach correspondingly high charges of energy. An immense counter-charge is set up, in favour of which all the other psychic systems are impoverished, so that a wide-spread paralysis or diminution of other psychic activity follows. We endeavour to learn from examples such as these to base our metapsychological conjectures on such prototypes. Thus from this behaviour we draw the conclusion that even a highly charged system is able to receive new energy streaming in, to convert it into a quiescent charge, thus to bind it psychically. The more intense is the intrinsic quiescent charge the greater is its binding force: and conversely the lower the charge of the system the less capable is it of receiving the energy that streams in, and so the more violent are the consequences when the barrier against stimuli is broken through. It is not a valid objection to this view that the intensifying of the charges round the place of irruption could be much more simply explained as the direct action of the oncoming mass of excitation. If that were so, the psychic apparatus would merely undergo an increase of its energy charges, and the paralysing character of pain, with the impoverishment of all the other systems, would remain without explanation. Nor do the very violent discharge effects of pain invalidate our explanation, for they happen in a reflex manner, that is to say, they follow without the interposition of the psychic apparatus. The indefinite nature of all the discussions that we term metapsychological naturally comes from the fact that we know nothing about the nature of the excitation-process in the elements of the psychic systems and do not feel justified in making any assumption about it. Thus we are all the time operating with a large X, which we carry over into every new formula. That this process is accomplished with energies which differ quantitatively is an easily admissible postulate, that it also has more than one quality (e. g. in the direction of amplitude) may be regarded as probable: the new consideration we have brought in is Breuers proposition that we have to do with two ways in which a system may be filled with energy, so that a distinction has to be made between a charging of the psychic systems (or its elements) that is free-flowing and striving to be discharged and one that is quiescent. Perhaps we may admit the conjecture that the binding of the energy streaming into the psychic apparatus consists in a translating of it from the free-flowing to the quiescent state.

I think one may venture (tentatively) to regard the ordinary traumatic neurosis as the result of an extensive rupture of the barrier against stimuli. In this way the old naïve doctrine of shock would come into its own again, apparently in opposition to a later and psychologically more pretentious view which ascribes aetiological significance not to the effect of the mechanical force, but to the fright and the menace to life. But these opposing views are not irreconcilable, and the psycho-analytic conception of the traumatic neurosis is far from being identical with the crudest form of the shock theory. While the latter takes the essential nature of the shock as residing in the direct injury to the molecular structure, or even to the histological structure, of the nervous elements, we seek to understand the effect of the shock by considering the breaking through of the barrier with which the psychic organ is provided against stimuli, and from the tasks with which this is thereby faced. Fright retains its meaning for us too. What conditions it is the failure of the mechanism of apprehension to make the proper preparation, including the over-charging of the systems first receiving the stimulus. In consequence of this lower degree of charging these systems are hardly in a position to bind the oncoming masses of excitation, and the consequences of the breaking through of the protective barrier appear all the more easily. We thus find that the apprehensive preparation, together with the over-charging of the receptive systems, represents the last line of defence against stimuli. For a great number of traumata the difference between the unprepared systems and those prepared by over-charging may turn the scale as to the outcome: with a trauma beyond a certain strength such a difference may no longer be of any importance. When the dreams of patients suffering from traumatic neuroses so regularly take them back to the situation of the disaster they do not thereby, it is true, serve the purpose of wish-fulfilment, the hallucinatory conjuring up of which has, under the domination of the pleasure-principle, become the function of dreams. But we may assume that they thereby subserve another purpose, which must be fulfilled before the pleasure-principle can begin its sway. These dreams are attempts at restoring control of the stimuli by developing apprehension, the pretermission of which caused the traumatic neurosis. They thus afford us an insight into a function of the psychic apparatus, which without contradicting the pleasure-principle is nevertheless independent of it, and appears to be of earlier origin than the aim of attaining pleasure and avoiding pain.

This is therefore the moment to concede for the first time an exception to the principle that the dream is a wish-fulfilment. Anxiety dreams are no such exception, as I have repeatedly and in detail shown; nor are the punishment dreams, for they merely put in the place of the interdicted wish-fulfilment the punishment appropriate to it, and are thus the wish-fulfilment of the sense of guilt reacting on the contemned impulse. But the dreams mentioned above of patients suffering from traumatic neuroses do not permit of classification under the category of wish-fulfilment, nor do the dreams occurring during psycho-analysis that bring back the recollection of the psychic traumata of childhood. They obey rather the repetition-compulsion, which in analysis, it is true, is supported by the (not unconscious) wish to conjure up again what has been forgotten and repressed. Thus the function of the dream, viz. to do away with the motives leading to interruption of sleep by presenting wish-fulfilments of the disturbing excitations, would not be its original one; the dream could secure control of this function only after the whole psychic life had accepted the domination of the pleasure-principle. If there is a beyond the pleasure-principle it is logical to admit a prehistoric past also for the wish-fulfilling tendency of the dream, though to do so is no contradiction of its later function. Now, when this tendency is once broken through, there arises the further question: are such dreams, which in the interests of the psychical binding of traumatic impressions follow the repetition-compulsion, not possible apart from analysis? The answer is certainly in the affirmative.

With regard to the war neuroses, so far as the term has any significance apart from a reference to the occasion of the appearance of the illness, I have explained elsewhere that they might very well be traumatic neuroses which have arisen the more easily on account of an ego-conflict.5 The fact mentioned above, viz. that a severe injury inflicted at the same time by the trauma lessens the chance of a neurosis arising, is no longer difficult to understand if two circumstances emphasised by psycho-analytic research are borne in mind. First that mechanical concussion must be recognised as one of the sources of sexual excitation (cp. the remarks: The effects of swinging and railway travelling in Drei Abhandlungen zur Sexualtheorie, 4. Auflage 1920); and, secondly, that a painful and feverish illness exerts for the time it lasts a powerful influence on the distribution of the libido. Thus the mechanical force of the trauma would set free the quota of sexual excitation which, in consequence of the lacking preparation by apprehension, has a traumatic effect: but, on the other hand, the contemporaneous bodily injury would bind the surplus excitation by the putting in of a claim to a narcissistic over-charging of the injured part (see Zur Einführung des Narzissmus, Sammlung kleiner Schriften zur Neurosenlehre, IV. Folge, 1918). It is also known, though the idea has not been sufficiently made use of in the Libido theory, that disturbances in the distribution of the libido so severe as those of melancholia may be removed for a time by an intercurrent organic disease; in fact even the condition of a fully developed dementia praecox is capable of a transitory improvement in these circumstances.